U.S. patent application number 16/293772 was filed with the patent office on 2020-09-10 for rotary disc filter having backwash guides.
This patent application is currently assigned to Veolia Water Solutions & Technologies Support. The applicant listed for this patent is Veolia Water Solutions & Technologies Support. Invention is credited to Johan Gustav Alexander Jibert, Per Larsson, Emil Svensson, Filip Thysell.
Application Number | 20200282345 16/293772 |
Document ID | / |
Family ID | 1000003984344 |
Filed Date | 2020-09-10 |
United States Patent
Application |
20200282345 |
Kind Code |
A1 |
Jibert; Johan Gustav Alexander ;
et al. |
September 10, 2020 |
ROTARY DISC FILTER HAVING BACKWASH GUIDES
Abstract
A rotary disc filter includes one or more filter discs secured
to a rotary drum and include a series of circumferentially spaced
backwash guides disposed in the filter disc. During backwashing,
the backwash guides function to engage a mixture of backwash and
suspended solids and guide or direct the mixture to a sludge trough
disposed in the disc filter. The backwash guides generally assure
that a greater percentage of the backwash and suspended solids
mixture end up in the solids trough.
Inventors: |
Jibert; Johan Gustav Alexander;
(Oxie, SE) ; Svensson; Emil; (Trelleborg, SE)
; Thysell; Filip; (Trelleborg, SE) ; Larsson;
Per; (Trelleborg, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Veolia Water Solutions & Technologies Support |
Saint-Maurice |
|
FR |
|
|
Assignee: |
Veolia Water Solutions &
Technologies Support
Saint-Maurice
FR
|
Family ID: |
1000003984344 |
Appl. No.: |
16/293772 |
Filed: |
March 6, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 33/76 20130101;
B01D 33/50 20130101; B01D 33/0074 20130101; C02F 1/004 20130101;
B01D 2201/084 20130101; B01D 33/0009 20130101 |
International
Class: |
B01D 33/76 20060101
B01D033/76; C02F 1/00 20060101 C02F001/00; B01D 33/00 20060101
B01D033/00; B01D 33/50 20060101 B01D033/50 |
Claims
1. A method of filtering a liquid and backwashing filter media in a
rotary disc filter, comprising: directing the liquid into a rotary
drum; directing the liquid from the rotary drum into one or more
filter discs secured to the rotary drum and having filter media
disposed on opposite sides of the filter disc; filtering the liquid
and removing suspended solids from the liquid by directing the
liquid from the filter disc outwardly through the filter media,
causing at least some of the suspended solids in the liquid to be
retained on an inner surface of the filter media; backwashing the
filter media by: rotating the drum and the filter disc such that
portions of the filter media are rotated into a position to be
backwashed by nozzles disposed exteriorly of the filter disc;
directing a backwash from the nozzles through the filter media and
into the interior of the filter disc and in the process, dislodging
at least some of the suspended solids retained on the inner surface
of the filter media which gives rise to a backwash and suspended
solids mixture in the filter disc; receiving the backwash and
suspended solids mixture in a series of backwash channels disposed
in the filter disc; and directing the backwash and suspended solids
mixture through the backwash channels and from the backwash
channels through openings in an inner periphery of the filter disc
and through openings in the drum and into a solids trough disposed
in the drum.
2. The method of claim 1 including backwashing the filter media as
the drum, filter disc and backwash channels are rotated; and as the
drum, filter disc and backwash channels are rotated, sweeping the
backwash and suspended solids mixture into the backwash
channels.
3. The method of claim 1 wherein, as the filter disc is rotated,
leading portions of the backwash channels are open in the direction
of travel.
4. The method of claim 1 wherein there is provided a series of
backwash guides associated with the backwash channels.
5. A rotary disc filter for filtering liquid comprising: a rotary
drum for receiving the liquid and having a plurality of openings
formed in a surface thereof; a solids trough disposed in the drum
and configured to receive a backwash and suspended solids mixture;
one or more filter discs secured to the drum and configured to
receive liquid from the drum and filter the liquid as the liquid
flows outwardly from the filter disc through filter media forming a
part of the filter disc; the filter disc including a plurality of
openings formed in an inner periphery of the filter disc; a
backwashing system for backwashing the filter media and including a
plurality of nozzles disposed exteriorly of the filter disc and
configured to direct a backwash through the filter media and into
the filter disc where the backwash dislodges suspended solids
retained on the filter media; a drive for rotatively driving the
drum and filter disc during a backwashing operation; a plurality of
backwash guides disposed in the filter disc and configured to
engage the backwash and suspended solids mixture during the
backwashing operation and to guide the backwash and suspended
solids mixture to the openings formed in the inner periphery of the
filter disc after which the backwash and suspended solids flow
through the openings in the drum and into the solids trough; the
backwash guides spaced inwardly from the filter media such that
open spaces are defined between the backwash guides and the filter
media; and wherein the backwash guides and the defined open spaces
are configured such that during the backwashing operation the
backwash and the suspended solids mixture flows through the open
spaces and through the filter disc to the openings formed in the
inner periphery of the filter disc.
6. The rotary disc filter of claim 5 wherein the backwash guides
are angled away from the filter media.
7. The rotary disc filter of claim 5 wherein the filter disc
comprises a filter frame and a series of filter segments supported
in the filter frame and wherein the backwash guides and the filter
segments form the open spaces that extend interiorly within the
filter disc.
8. The rotary disc filter of claim 5 wherein the backwash guides
disposed in the filter disc include pairs of backwash guides that
are transversely aligned and include terminal edges that terminate
in spaced apart relationship with respect to each other.
9. The rotary disc filter of claim 5 wherein the filter disc
comprises a filter frame and a plurality of filter segments
supported in the filter frame; and wherein the backwash guides are
secured to or integrally formed with the filter frame and project
therefrom into the filter disc.
10. The rotary disc filter of claim 5 wherein the open spaces form
at least a part of a series of backwash channels that extend
through the filter disc, the backwash channels having an open side
that faces the direction of travel of the filter disc during the
backwashing operation.
11. The rotary disc filter of claim 10 wherein the backwash
channels extend between an outer periphery of the filter disc and
the inner periphery of the filter disc, and wherein the backwash
channels include inner end portions that terminate adjacent the
openings in the inner periphery of the filter disc.
12. A rotary disc filter for filtering a liquid comprising: a
rotary drum for receiving the liquid and having a plurality of
openings formed in a surface thereof; a solids trough disposed in
the drum and configured to receive a backwash and suspended solids
mixture; one or more filter discs secured to the drum and
configured to receive liquid from the drum and filter the liquid as
the liquid flows outwardly from the filter disc through filter
media forming a part of the filter disc; the filter disc including
a plurality of openings formed in an inner periphery of the filter
disc; a drive for rotatively driving the drum and causing the
filter disc to rotate with the drum; a backwash system for
backwashing the filter media and including a plurality of nozzles
disposed exteriorly of the filter disc and configured to direct the
backwash through the filter media and into the filter disc where
the backwash dislodges suspended solids from the filter media and a
backwash and suspended solids mixture is formed; a plurality of
backwash guides that project inwardly from opposite sides of the
filter disc into the interior of the filter disc; the backwash
guides and a portion of the filter disc form a series of backwash
channels that extend through the filter disc; wherein the backwash
channels extend generally toward the openings in the inner
perimeter of the filter disc; and wherein in a backwashing
operation, the backwash channels are configured to receive at least
a portion of the backwash and suspended solids mixture and to
direct the backwash and the suspended solids to the openings in the
inner perimeter of the filter disc where the backwash and suspended
solids pass through the openings in the drum and into the solids
trough.
13. The rotary disc filter of claim 12 wherein the backwash guides
include terminal edges that terminate intermediately between
opposite sides of the filter disc.
14. The rotary disc filter of claim 12 wherein the backwash guides
projecting from one side of the filter disc are transversely
aligned with backwash guides projecting from the other side of the
filter disc.
15. The rotary disc filter of claim 14 wherein the transversely
aligned backwash guides are spaced apart such that an open area is
defined between the transversely aligned backwash guides.
16. The rotary disc filter of claim 12 wherein the backwash
channels extend generally between the outer and inner peripheries
of the filter disc, and wherein the backwash channels include inner
end portions and wherein the inner end portions of the backwash
channels terminate adjacent the openings in the inner periphery of
the filter disc.
17. The rotary disc filter of claim 12 wherein the backwash
channels are disposed in pairs with the pairs of backwash channels
being transversely aligned and circumferentially spaced around the
filter disc.
18. The rotary disc filter of claim 12 wherein the filter disc
comprises a filter frame that supports the filter media on opposite
sides thereof; and wherein the backwash guides are secured to or
integrally formed with the filter frame and project inwardly
therefrom into the filter disc.
19. The rotary disc filter of claim 18 wherein the filter media
comprises a series of filter segments supported in the filter frame
and wherein the filter segments and the filter frame form a series
of compartments around the filter disc; and wherein the backwash
guides and the backwash channels are formed on leading edges of the
compartments.
20. The rotary disc filter of claim 12 wherein the backwash guides
that project from opposite sides of the filter disc include
elongated edges that angle inwardly with respect to the filter
media.
21. A rotary disc filter for filtering liquid comprising: a rotary
drum for receiving the liquid and having a plurality of openings
formed in a surface thereof; a solids trough disposed in the drum
and configured to receive a backwash and suspended solids mixture;
one or more filter discs secured to the drum and configured to
receive the liquid from the drum and to filter the liquid as the
liquid flows outwardly from the filter disc through filter media
forming a part of the filter disc; the filter disc including a
filter frame; a drive for rotatively driving the drum and causing
the filter disc to rotate with the drum during a backwashing
operation; a plurality of circumferentially spaced backwash guides
projecting from the filter frame into the interior of the filter
disc and configured to engage the backwash and suspended solids
mixture and facilitate the movement of the backwash and suspended
solids mixture into the solids trough; the backwash guides being
angled relative to an adjacent side of the filter disc and
projecting in the general direction of rotation of the filter disc
during a backwashing operation; and the backwash guides including
elongated edges that terminate intermediately between opposite
sides of the filter disc.
22. The rotary disc filter of claim 21 wherein the backwash guides
form a part of a plurality of backwash channels configured to
direct or channel the backwash and suspended solids mixture through
the filter disc.
23. The rotary disc filter of claim 21 wherein the backwash guides
are disposed in pairs within the filter disc and wherein each pair
of backwash guides are transversely aligned and project inwardly
towards each other where the elongated edges terminate in spaced
apart relationship to form an opening between transversely aligned
backwash guides.
24. The rotary disc filter of claim 21 wherein the filter frame
includes a plurality of circumferentially spaced support arms and
wherein the backwash guides project from a leading side of the
support arms.
25. The rotary disc filter of claim 21 wherein the backwash guides
are spaced inwardly from the filter media.
26. The rotary disc filter of claim 21 wherein, based on FIG. 1B, L
is 5-85 mm, H is 3-40 mm, and .phi. is 2.degree.-83.degree.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to rotary disc filters that
filter water or wastewater.
BACKGROUND OF THE INVENTION
[0002] Rotary disc filters are designed to filter a liquid, such as
water or wastewater, and typically include a drum, a plurality of
filter discs secured to the drum, and a backwash system for
backwashing filter media forming a part of the filter disc. Liquid
to be filtered passes from the drum into the filter disc, which
includes the filter media on opposite sides thereof. Liquid in the
filter disc flows outwardly through the filter media. In this
process, suspended solids in the liquid are captured or retained on
the inner surfaces of the filter media. From time-to-time, the
filter media is cleaned by a backwashing operation. In the
backwashing operation, nozzles disposed exteriorly of the filter
disc direct a pressurized backwash through the filter media and
into the filter disc. The backwash dislodges the suspended solids
retained on the inner surfaces of the filter media. The mixture of
backwash and dislodged suspended solids flow by gravity from the
filter disc, through openings in the drum, and into a solids trough
disposed in the drum.
[0003] It is challenging, however, to channel all or substantially
all of the suspended solids into the solids trough. An accumulation
of suspended solids takes place inside the drum and inside the
filter disc. Particles of all sizes accumulate in these areas. The
reasons for this accumulation are many. A main reason is that 100%
of the solids filtered by the filter media do not end up in the
solids trough. Some of the solids fall off the media when breaking
through the water surface when the drum and filter disc are rotated
in a backwashing operation. Other suspended solids fail to reach
the solids trough due to a high incoming water speed or a high
rotation speed of the filter disc during backwashing. Further, some
of the suspended solids captured or retained on the filter media do
not end up in the solids trough. All of this tends to result in an
inefficient filtering process.
[0004] Therefore, there has been and continues to be a need for a
rotary disc filter that is designed to more efficiently collect
suspended solids and direct them into the solids trough.
SUMMARY OF THE INVENTION
[0005] The present invention entails a rotary disc filter having
backwash guides that are designed to guide a backwash and suspended
solids mixture through the filter disc and through openings in the
inner periphery of the filter disc after which the backwash and
suspended solids pass through openings in the drum and into the
solids trough disposed in the drum.
[0006] In one embodiment, the backwash guides project inwardly from
opposite sides of the filter disc and are circumferentially spaced
around the filter disc. Backwash guides and the filter media
disposed on opposite sides of the filter disc form a series of
backwash channels that extend generally between the inner and outer
peripheries of the filter disc. Inner end portions of the backwash
channels are disposed adjacent openings in the inner periphery of
the filter disc. As the filter disc is rotated during the
backwashing operation, the backwash channels tend to catch or
receive the mixture of backwash and suspended solids and guide the
mixture of backwash and suspended solids along the backwash
channels and into the openings formed in the inner periphery of the
filter disc. Thereafter, the backwash and suspended solids mixture
pass through openings in the drum and into the solids trough
disposed within the drum.
[0007] Other objects and advantages of the present invention will
become apparent and obvious from a study of the following
description and the accompanying drawings which are merely
illustrative of such invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a cross-sectional view of a disc filter.
[0009] FIG. 1A is an enlarged fragmentary view illustrating a
portion of a filter disc that forms a part of the disc filter.
[0010] FIG. 1B shows a portion of FIG. 1A and identifies the
location of dimension and angle indicators L, H and cp.
[0011] FIG. 2 is a schematic cross-sectional view of a portion of
the filter disc particularly illustrating the backwash guides.
[0012] FIG. 3 is a perspective view of a filter frame module having
the backwash guides incorporated therein.
[0013] FIG. 4 is a perspective view of the disc filter with
portions broken away to better illustrate certain components of the
disc filter.
[0014] FIG. 5 is a perspective view of a rear portion of the disc
filter with portions broken away to better illustrate certain
components of the disc filter.
[0015] FIG. 6 is a fragmentary perspective view of a portion of the
disc filter which illustrates how the backwash guides facilitate
the removal of a backwash and suspended solids mixture from the
filter disc.
DESCRIPTION OF EXEMPLARY EMBODIMENT
[0016] With further reference to the drawings and as discussed
above, the present invention relates to a rotary disc filter 10
that is designed to effectively collect suspended solids in a
solids trough 14. This is achieved by a series of backwash guides
12 provided in filter discs 16 mounted to a rotary drum 40. See
FIGS. 1, 1A and 2. Each filter disc 16 comprises a filter frame 18
and filter segments 20 supported in the filter frame. Filter
segments 20 form filter media disposed on opposite sides of the
filter disc 16. See FIG. 2. Backwash guides 12 are spaced inwardly
from the filter segments 20. This spacing results in the backwash
guides 12, filter frame and the filter segments 20 forming backwash
channels 22 around the interior of the filter disc 16.
[0017] In a backwashing operation, the filter discs 16 and hence
the backwash channels 22 are rotated past backwashing nozzles 32
that form a part of the backwashing system 30 and which are
disposed on opposite sides of the filter discs 16. Pressurized
backwash from the nozzles 32 penetrates the filter segments 20 and
enters the filter discs 16, and in the process, suspended solids
are dislodged from an inner side of the filter segments 20.
Backwash that penetrates the filter segments 20 does not typically
continue in the same direction once inside the filter disc 16. The
velocity of the backwash on the inner side of the filter segment 20
is relatively low. The backwash which penetrates the filter media
tends to run down, by gravity, along the inner sides of the filter
media. Expressed in another way, the backwash and suspended solids
mixture tends to move by gravity closely adjacent the inner
surfaces of the filter segments 20. Backwash channels 22 include
open sides that face the direction of rotation of the filter discs
16. As portions of the filter segments 20 move towards and past the
backwashing nozzles 32, the backwash channels 22 tend to catch or
scoop the mixture of backwash and suspended solids. Since a
substantial portion of the backwash and suspended solids mixture
moves adjacent the inner surfaces of the filter segments 20, this
facilitates the efficient capture of the mixture. Due to the
location of the nozzles 32 and the direction of rotation of the
filter disc 16, as viewed for example in FIG. 1, the backwash and
suspended solids mixture tend to move towards and into oncoming
backwash channels 22. Once in the backwash channels 22, the
backwash and suspended solids mixture is guided inwardly to and
through openings 18D formed in the inner periphery 18B of the
filter frame 18. From there, the mixture of backwash and suspended
solids passes through openings 40A in the drum 40 and into the
solids trough 14 disposed in the drum.
[0018] Subsequently, the basic structure and function of the disc
filter 10 will be described. But first, the focus is on the filter
discs 16 and the backwash guides 12. FIGS. 1 and 1A show a filter
disc 16 mounted to the rotary drum 40. Drum 40 includes an array of
openings 40A formed in the surface thereof. Each filter disc 16
comprises a filter frame 18 and the filter segments 20 supported in
the filter frame. In the embodiment shown in FIG. 1, the filter
frame 18 comprises a plurality of circumferentially spaced support
arms 18A. Support arms 18A extend between an inner periphery 18B
and an outer periphery 18C of the filter frame. Inner periphery 18B
of the filter frame 18 also forms the inner periphery of the filter
disc 16. Openings 18D are formed in the inner periphery of the
filter disc 16. Openings 18D enable water or liquid to flow from
the drum 40 into the filter discs 16 during the filtering process.
They also allow a mixture of backwash and suspended solids to flow
from the filter discs 16 through openings 40D in the drum 40 and
into the solids trough 14 disposed in the drum. See FIG. 1.
[0019] As noted above, in one embodiment during a backwashing
operation, filter discs 16 rotates counterclockwise as viewed in
FIG. 1. Backwash guides 12 project from one side of the support
arms 18A in the direction of rotation of the filter discs 16.
Backwash guides 12 can be integrally formed with the filter frame
18 and particularly with the support arms 18A attached or fastened
to a particular filter frame structure or integrally formed with
the filter segment 20.
[0020] During a backwashing operation, the nozzles 32 are disposed
exteriorly of the filter discs 16 and direct a pressurized backwash
through the filter segments 20. In the process, suspended solids
filtered by the filter segments 20 and retained on the inner side
thereof are dislodged. This results in a mixture of backwash and
suspended solids in the filter discs 16. The function of the
backwash guides 12 and backwash channels 22 is to guide the mixture
of backwash and suspended solids out of the filter discs 16 and
into the solids trough 14.
[0021] To better illustrate the backwash guides 12 and how they
facilitate the efficient capture and removal of the backwash and
suspended solids mixture, reference is made to FIG. 2. FIG. 2 is a
schematic cross-sectional illustration showing a portion of the
filter frame 18, filter segments 20 and the backwash guides 12. As
noted above, filter frame 18 includes support arms 18A and they are
schematically illustrated in FIG. 2. Support arms 18A include an
inner portion 18A1, an outer portion 18A2, and a cross portion
18A3. See FIG. 2. Again, this is a schematic illustration and in
one embodiment the transversely aligned support arms 18A shown in
FIG. 2 can be interconnected. In any event, the support arms 18A
form back-to-back grooves that receive and hold seals 54. Filter
segments 20 which include a surrounding frame and filter media are
in turn received and held in the seals 54.
[0022] Continuing to refer to FIG. 2, the backwash guides 12
project from one end of the inner portions 18A1. Again, the
backwash guides 12 project in the direction of rotation of the
filter discs 16 during backwashing as shown in FIGS. 1 and 2. Note
that the backwash guides 12 also project inwardly into the filter
disc 16. Further, the backwash guides 12 are circumferentially
spaced around the filter disc 16. Backwash guides 12 are arranged
in pairs. That is, two backwash guides 12 are transversely aligned
and disposed across from each other. See FIG. 2. The backwash
guides 12 project slightly towards each other. This forms an open
space 60 between each pair of backwash guides 12. This open space
enables water or liquid to pass through the open space when the
filter discs 16 are rotated.
[0023] Backwash guides 12 in one embodiment effectively form an
elongated edge that extends between the inner and outer peripheries
18B and 18C of the filter frame 18. Further, the backwash guides
12, along with portions of the support arms 18A, seals 54 and
filter segments 20 form the backwash channels 22. See FIG. 2.
During a backwashing operation, the backwash channels 22
effectively entrap a mixture of backwash and suspended solids and
guide or direct the mixture to openings 18D formed in the inner
periphery 18B of the filter frame 18. As noted before, this enables
the backwash and suspended solids mixture to pass through the array
of openings 40A in the drum 40 and into the underlying solids
trough 14.
[0024] As noted above, during a backwashing operation, the drum 40
and the filter discs 16 can be rotated. Filter segments 20 are
rotated to an upper position on the disc filter 10 where the
nozzles 32 are stationed. As the backwash guides 12 approach the
nozzles 32 and move past the nozzles, backwash from the nozzles 32
penetrate the filter segments 20 and enter the interior of the
filter discs 16. When this happens, the backwash and dislodged
suspended solids form a mixture. The backwash guides 12 tend to
urge the backwash and suspended solids mixture into the backwash
channels 22. The backwash guides 12 and the backwash channels 22
tend to catch or scoop the backwash and suspended solids mixture
that ends up inside the filter disc 16. Once in the backwash
channels 22, the backwash and suspended solids mixture is directed
along the channels 22. Inner portions of the backwash channels 22
terminate adjacent the openings 18D in the inner periphery 18B of
the filter frame or filter disc. Thus, the backwash channels 22
effectively guide or direct the backwash and suspended solids
mixture into the openings 18D of the filter frame 18. From there,
as discussed above, the backwash and suspended solid mixture passes
through openings 40A in the drum 40 and into the solids trough
14.
[0025] In some embodiments, the filter frame 18 is modular and is
constructed of interchangeable modules. The modules can be
constructed of plastic or other suitable materials. With reference
to FIG. 3, there is shown therein one of the modules 80 employed in
the filter frame 18 shown in FIG. 1. In this example, the module 80
is constructed of plastic and includes a base 82. Bases 82 of the
modules form the inner periphery 18B of the filter frame 18. Note
that the bases 82 are interconnected in back-to-back relationship
and secured around and to the drum 40. Each base 82 includes
openings on opposite sides. These openings form openings 18D in the
inner periphery 18B of the filter frame. Extending upwardly from
the bases 82 are the support arms 18A that has been discussed
above. As seen in FIG. 1, outer covers 86 are interconnected
between adjacent modules 80. Thus, the modules 80, along with the
outer covers 86, form the filter frame 18 shown in FIG. 1.
[0026] Formed on opposite sides of each module 80 is a pair of
filter grooves. These filter grooves receive the surrounding frames
of respective filter segments 20. A seal can be interposed between
the filter segments 20 and the filter grooves.
[0027] FIG. 3 depicts one way in which the backwash guides 12 can
be incorporated into the modules 80. Note that a pair of backwash
guides 12 extends along a leading side of the support arms 18A of
the modules 80. In particular, each backwashing guide 12 is
integrally formed with a portion of the support arms 18A and
projects slightly inwardly therefrom in the manner illustrated in
FIG. 2. Therefore, on the leading side of each support arm 18A
there is provided a pair of backwash guides 12 that extend over a
substantial length of the support arms 18A. Note that these
backwash guides 12, in conjunction with the modules 80 and the
filter segments 20, also form a pair of backwash channels 22 on
leading sides of the support arms. Backwash channels 22 include
inner terminal ends that terminate adjacent the openings in the
bases 82. Thus as described above, during a backwashing operation
backwash channels 22 function to guide and direct a mixture of
backwash and suspended solids to the openings formed in the bases
82 of the modules 80. And like discussed above, the openings in the
bases 82 are aligned with openings 40A of the drum 40 and hence the
backwash and suspended solids mixture passing from the openings in
the bases 82 flows through the openings 40A into the underlying
solids trough 14.
[0028] The volume and dimensions of the backwash channels 22 can
vary. This is especially the case because the width of the filter
disc 16 varies from one disc filter to another. FIG. 1B uses L, H
and .phi. to denote dimensions and an angle relative to the
backwash guides 12. Again, the length of L and H, as well as the
angle .phi., will vary. However, in exemplary embodiments, L would
typically be 5-85 mm, H 3-40 mm, and .phi.
2.degree.-83.degree..
[0029] FIG. 6 illustrates how the backwash guides 12 and the
backwash channels 22 facilitate the recovery of the backwash and
suspended solids mixture and how they guide and direct the mixture
into the solids trough 14. The flow of the backwash and suspended
solids mixture is shown by heavy dotted lines and arrows in FIG. 6.
FIG. 6 does not show the backwash channels 22. The dotted lines and
arrows are meant to simply represent the flow of the backwash and
suspended solids mixture through the respective filter discs 16.
Note also in FIG. 6 where the flow of the mixture passes through
openings 18D in the inner periphery of the filter frame and from
there through the array of openings 40A formed in the drum and then
into the underlying solids trough 14.
[0030] The filter discs 16, drum 40, along with the backwash guides
12 and the backwash channels 22 are incorporated into a disc filter
10. It may be beneficial to briefly review the basic design of an
exemplary disc filter. The disc filter 10, shown in FIGS. 4 and 5,
includes a housing. Some rotary disc filters (a second type) are
not provided with a substantial housing structure. These disc
filters are often referred to as frame-type disc filters as they
are designed to be installed in a pre-formed concrete basin. There
is yet a third type or version of a disc filter which includes a
half tank or frame with a bottom and sides and which only reaches
to about the center of the drum of the disc filter.
[0031] In any event, either type of disc filter is provided with a
frame structure for supporting various components that make up the
disc filter. In this regard, the drum 40 is rotatively mounted on
the frame structure of the disc filter. Generally the drum 40 is
closed except that it includes an inlet opening and the array of
openings 40A discussed above. The filter discs 16 are secured to
the drum 40 and rotatable therewith during a backwashing operation.
During the filtering of water or liquid, influent water or liquid
is directed into the inlet of the drum 40 and from the drum into
the filter discs 16 secured on the drum. The number of filter discs
16 secured to the drum can vary. A water holding area is defined
inside each filter discs 16 for receiving and holding water or
liquid to be filtered by the disc filter 10. Head pressure
associated with the influent liquid or water is effective to cause
the water or liquid to flow outwardly from the filter discs 16 and
through the filter segments 20. Water exiting the filter discs 16
is filtered water or filtrate. As discussed above, this results in
suspended solids in the water or liquid being captured or retained
on the inner surfaces of the filter segments 20.
[0032] Filtered water or liquid exiting the filter discs 16 is
collected in a holding chamber that underlies the filter discs.
This holding chamber or area includes an outlet that enables the
filtered water or liquid to be discharged from the disc filter
10.
[0033] During the backwashing operation, it is necessary for the
drum 40 and the filter discs 16 mounted thereon to rotate. Disc
filter 10 is provided with a drive system for rotatively driving
the drum 40 and the filter discs 16. In the case of the embodiment
illustrated in FIGS. 4 and 5, mounted to a panel or wall structure
about the back portion of the disc filter 10 is a drum motor 90
that is operative to drive a sprocket or sheave connected to a
shaft on which the drum 40 is mounted. See FIG. 5. Various means
can be operatively interconnected between the drum motor 90 and the
sprocket or sheave for rotating the drum 40. In one example, a
chain drive is utilized to drive a sprocket secured to the shaft
that rotates the drum 40. Various other types of drive systems can
be utilized to rotate the drum and the filter discs 16. In some
cases, for example, there may be a direct drive on the drum shaft
from a gear motor.
[0034] Returning to the backwash system 30 discussed above, the
system comprises a backwash pump 33, a manifold 34 that extends
along a side portion of the disc filter 10, and a series of feed
tubes 35 connected to the manifold 34 and projecting inwardly
therefrom. Feed tubes 35, sometimes referred to as inner pipes,
project from the manifold 34 into areas between respective filter
discs 16. Secured to the feed tubes 35 are a series of nozzle
holders or nozzle bars 36. Nozzles 32 are mounted on the nozzle
bars 38. In a preferred embodiment, the backwash pump 33 forms a
part of the disc filter. In other embodiments, pressurized backwash
can be provided from a source other than a backwash pump that forms
a part of the disc filter 10.
[0035] Manifold 34 can be rigidly mounted or rotatively mounted
along one side of the disc filter 10. In some cases, manifold 34 is
operatively connected to a drive (not shown) that can be indirectly
driven from the drum motor 90. In any event, the manifold 34,
during a cleaning operation, can oscillate back and forth, which
results in the nozzles 32 sweeping back and forth between the
filter discs 16 so as to backwash particular areas of the filter
segments 20 disposed on opposite sides of the filter discs 16. In
other cases, the manifold 24 is rigidly mounted and does not
oscillate back and forth during the backwashing operation.
[0036] There are many advantages to the backwash guides 12. They
assure that a larger percentage of the backwash and suspended
solids mixture end up in the solids trough 14. One measure of the
effectiveness of the backwash guides 12 can be appreciated from
examining what is referred to herein as "separation speed of
suspended solids" (mg separated suspended solids/s). In order to
determine the separation speed of suspended solids, the first step
is to measure the flow of the backwash and suspended solids mixture
being discharged by the disc filter 10. Secondly, a sample of the
flow of the backwash and suspended solids mixture is taken and a
total suspended solids (TSS) test is carried out which gives the
concentration of suspended solids (mg/L) of the backwash and
suspended solids mixture. The separation speed of the suspended
solids is defined as the product of the flow and the suspended
solids concentration. The employment of the backwash guides 12
will, in most cases, increase the separation speed of the suspended
solids.
[0037] "Configured to" is used in this application. The term
"configured to" means "designed to".
[0038] The present invention may, of course, be carried out in
other specific ways than those herein set forth without departing
from the scope and the essential characteristics of the invention.
The present embodiments are therefore to be construed in all
aspects as illustrative and not restrictive and all changes coming
within the meaning and equivalency range of the appended claims are
intended to be embraced therein.
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